Q: How do you cook and cool in the same machine?

A: Blentech has a great deal of experience designing and constructing thermal processing vessels that can perform both cooking and cooling. Blentech cookers are heated either directly, via steam injection into the product, or indirectly through a jacket designed to accept pressurized steam, hot water or thermal oil.

We also support direct and indirect methods of cooling. Cryogens (CO2 or Nitrogen) can be applied onto the product for very rapid direct contact cooling. Generating a vacuum in the vessel chamber creates an evaporative cooling effect that draws heat out of the batch. Finally, chilled water or glycol indirectly cools products when circulated through a jacket designed to accept both steam and liquid cooling media.

The entire “cook-chill” process is fully automated via Blentech's AutoChef PLC-based operating control system with user-friendly modular recipe capability. The selection and combination of heating and cooling methods used is determined by product characteristics and specifications of a particular application.

Q: How does vacuum cooling work?

A: Vacuum cooling can be a surprisingly fast and effective means of cooling for a wide range of food products - all that is needed is sufficient free moisture in the batch to support the process. Two stage vacuum cooling packages can cool products to 85°F (40°C) while three stage systems can cool to 40°F (5°C). Blentech's patented ComboChill process combines the benefits of jacket cooling with vacuum cooling for products with very sensitive flavor profiles. Learn more about vacuum cooling here.

Q: How long do scrapers last?

A: Blentech offers its scraper system in three standard material types: Nylon, Polypropylene and high temperature resistant Peek-based polymer, each satisfies the requirements of a particular range of products and applications. Each material has its own wear characteristics and expected life before the scraper must be replaced: Nylon (~1,000 hours), Polypropylene (~5-600 hours) and Peek-based polymer (~1200 hours).

The actual effective scraper life will vary based on the relative abrasiveness of the product(s) being cooked as well as the process operating parameters (agitator speed, etc.). Caustic cleaning solutions can also attack the scraper material over time, particularly if used in high concentrations.

[Hint: Blentech scrapers perform with equal effectiveness in either agitation rotational direction. To get more life out of a set of scrapers, make sure that your are taking advantage of Blentech's auto-reversing agitation feature to agitate during processing in both the forward and reverse directions. This will allow the scrapers to wear more evenly while improving product particulate integrity.]

[NOTE: Never operate the agitator(s) of a Blentech batch or continuous thermal processor that is outfitted with scrapers without first filling the vessel with a minimum of 4-6 inches of water to act as a lubricant. Running the agitators dry will cause damage to both the scrapers and the trough of the vessel.]

Q: How do I determine when to replace my scrapers?

A: When a Blentech cooker with scrapers is operated using the auto-reversing agitation, a signature oval pattern will begin to develop on the bottom of the scrapers. The scrapers continue to function while they wear though they will gradually lose their effectiveness as the oval pattern narrows. When the width of this oval becomes less than 50% of the width of the entire scraper, it is recommended that you replace your scraper set.

If you are observing product build-up and burn-on across the jacket heat transfer surface, which was not observed when the scraper set was new, this is a second indication of excessively worn scrapers. [Note: If you notice build-up or burn-on only beneath a single scraper track, this indicates a scraper that, for some reason, is no longer properly pre-tensioned against the jacket surface. Contact your dealer or Blentech Technical Service to report this situation.

Q: My product is taking longer to cook than I think it should?

A: Unduly long batch cooking cycle times (or heating sluggishness and the inability to hold temperature on continuous cookers) are often a symptom of a flooded steam jacket. The steam pressure gauge on the jacket will indicate pressure in the jacket, even if the jacket contains pressurized hot water, not steam, which will transfer heat very poorly, if at all. This can occur when either a) there is excessive condensate in the steam supply line to the cooker or b) the rise and run of the condensate return line cause line head pressure sufficient to overcome the ability of the steam in the jacket to push the condensate back to the boiler. In this case, installation of a condensate pump is specified.

A condensate trap has a limited ability to pass the large amounts of condensate that may be present in the steam line at the beginning of a production day/shift. It is recommended that a condensate blow-down valve be installed ahead of the steam valve at the cooker to enable condensate in the line to be purged before beginning production.